Note: Descriptions are shown in the official language in which they were submitted.
CA 02259862 2008-10-23
TRAILER VEHICLE
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wheeled
vehicles and, more particularly, pertains to a
wheeled vehicle adapted to be towed by a motive
vehicle, such as a tractor.
2. Description of the Prior Art
United States Patent No. 5,595,397, issued
January 21, 1997 to Applicant discloses a steerable
trailer vehicle having a main frame portion to which
a rear frame portion carrying at least one pair of
steerable wheels is pivotally mounted. A front frame
portion is pivotally connected to the rear frame
portion and is supported on the ground by two sets of
wheels. The rear steerable wheels are controlled by a
hydraulic system which is designed to be responsive
to a turning movement of the motive vehicle to cause
the rear wheels to trace an arc similar to an arc
traced by the motive vehicle.
Although the steering system of the trailer
vehicle described in the above mentioned patent is
efficient, it has been found that there is a need for
a new mechanical steering system which does not
necessitate the utilisation of hydraulic circuits.
Furthermore, it would be highly beneficial
to provide a suspension system which is adapted to
attenuate the noise generated by the collision of the
frame elements which are pivotally connected to each
other.
Finally, it has been found that although
the arrangement of the pivots and axles of the
trailer vehicle described in the above mentioned
patent is generally satisfactory, there is a need for
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a new pivot and axle arrangement which is adapted to
enhance the distribution of the weight and the load
supported by the trailer vehicle.
SUMMARY OF THE INVENTION
It is therefore an aim of the present
invention to provide a trailer vehicle having a new
mechanical steering system.
It is also an airn of the present invention
to provide a trailer vehic _e having a new suspension
mechanism.
It is still an aim of the present invention
to provide a trailer vehicle having pivot shafts and
axles which are arranged to efficiently distribute
the weight of the vehicle and the load carried
thereon.
Therefore, in accordance with the present
invention, there is provided a trailer vehicle
comprising a frame structure having a longitudinal
axis and a forward end portion, at least one set of
steerable wheels pivoted to said frame structure, a
forward articulated extension provided at the forward
end portion of the frame structure and adapted to be
coupled to a motive vehicle such as to be responsive
to a turning movement of the motive vehicle, link
means connected to the forward articulated extension
for communicating a rotary movement to crank means
mounted to the frame structure in response to an
angular movement of the forward articulated
extension, and steering linkage means laterally
displaceable by the crank means to cause the set of
steerable wheels to trace the arc traced by the
motive vehicle.
In a further construction in accordance
with the present invention, the trailer vehicle
comprises a frame structux-e having a longitudinal
axis, at least one set of steerable wheels carried by
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the frame structure, a hitch pole extending forwardly
of the frame structure, the hitch pole having a
forward articulated extension adapted to be mounted
to a hitch of a motive vehicle such as to be
responsive to a turning movement of the motive
vehicle, link means coiinected to the forward
articulated extension for communicating a rotary
movement to a pivot assembly mounted to the hitch
pole about a pivot axis at right angles to the
longitudinal axis of the frame structure in response
to an angular movement of' the forward articulated
extension, rotatable shaft means mounted to the frame
structure and extending axially thereof between the
set of steerable wheels, the rotatable shaft means
being drivingly connected to the pivot assembly,
crank means mounted to the rotatable shaft means for
rotation therewith, and steering linkage means
connecting the crank means and the set of steerable
wheels together, whereby angular movement of the
forward articulated extension will cause rotary
movement of the pivot assembly and conjoint rotation
of the rotatable shaft means and the crank means
thereby imparting lateral displacement to the
steering linkage means, causing the set of wheels to
trace the arc traced by the motive vehicle.
In accordance with a general aspect of the
present invention, there is provided a trailer
vehicle including a frame structure having a forward
end adapted to be coupled to a motive vehicle. The
frame structure includes an axle extending laterally
thereof. Each end of the axle pivotally mounts
respective first beams. The frame structure further
includes a transversal wheel mounting beam adapted to
support at least one wheel at each end thereof, the
transversal wheel mounting beam being connected to
the first beams by bracket rneans pivoted to pin means
received in slot means defined at one end of the
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first beams, and biasing means for normally
preventing the transversal wheel mounting beam from
pivoting away from the first beams.
In accordance with another general aspect
of the present invention, there is provided a trailer
vehicle including a frame structure having a forward
end adapted to be coupled to a motive vehicle, the
frame structure including an axle extending laterally
thereof for pivotally supporting a first frame
portion carrying at least one set of wheels, a second
frame portion connected to a front end portion of the
first frame portion by a pivot, and a set of
intermediate wheels and a set of front wheels
journaled to the second frame portion on opposed
sides of the pivot, wherein the pivot is disposed
relative to the axle such as to support about 60% to
about 70% of the mass carried by the trailer vehicle,
the remaining of the mass being supported by the
wheels journaled to the first frame portion.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature
of the present invention, reference will now be made
to the accompanying drawings, showing by way of
illustration a preferred embodiment thereof, and in
which:
Fig. 1 is a schematic top plan view of a
trailer vehicle in accordance with the present
invention;
Fig. 2 is a schematic side elevational view
of the trailer vehicle shown in Fig. 1;
Fig. 3 is an enlarged fragmentary rear view
of a detail of the present invention;
Fig. 4 is a vertical cross-section taken
along line 4-4 of Fig. 1;
Fig. 5 is a vert_Lcal cross-section similar
to Fig. 4 showing different. operating positions of a
suspension mechanism of the trailer vehicle;
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Fig. 5a is a vertical cross-section similar
to Fig. 4, but showing a variant of the present
invention;
Fig. 6 is a fragmentary enlarged top plan
view of a hitch pole of the trailer vehicle;
Fig. 7 is a vertical cross-section taken
along line 7-7 of Fig. 6;
Fig. 8 is a fragmentary enlarged top plan
view of a rear wheel steering mechanism of the
trailer vehicle;
Fig. 9 is a fragmentary enlarged top plan
view of the trailer vehicle showing a detail thereof;
Fig. 10 is a fragmentary front plan view of
a further detail of the trailer vehicle;
Fig. 11 is a schematic top plan view of a
trailer vehicle in accordance with another embodiment
of the present invention; and
Fig. 12 is a top plan view of a front
portion of a trailer vehicle illustrating a possible
location of a pivot assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now referring to the drawings, and in
particular to Fig. 1, a trailer vehicle in accordance
with the present invention and generally designated
by numeral 10 will be described.
The trailer vehicle 10 generally includes a
main frame 12 comprising two elongated lateral right
angle rails 14a and 14b corinected to each other by a
number of transversal members 15, 16 and 18. The
rails 14a and 14b are configured to support a tank
(not shown) or the like. The tank may be removably
mounted to the rails 14a and 14b by means of brackets
(not shown).
A hitch pole 20 having a V-shaped
configuration is pivotally mounted to a pair of
brackets 22a and 22b depending from respective under
surfaces of the rails 14a and 14b, as seen in Fig. 2.
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Adjustment bolts 23 are provided at each end of the
transversal member 15 to secure the hitch pole 20
into different angular, vertical positions relative
to the main frame 12. The adjustment bolts 23 are
threadably engaged to the threaded ends of two U-
shaped members (not shown) extending under and on the
inner and outer sides of the left and right branches
of the hitch pole 20 and. through the transversal
frame member 15. Thus, the hitch pole 20 is thereby
attached to the opposed ends of the transversal
member 15. Spacers (not shown) may be inserted
between the main frame 12 and the hitch pole 20 to
position the latter into a pre-selected angular
position relative to the ma:in frame 12.
As seen in Fig. 2, an axle 24 is mounted to
the main frame 12 interrially of the transversal
member 18 by means of a pa:ir of lateral brackets 25a
and 25b extending downwardly from the rails 14a and
14b, respectively. Longitudinally extending beams 26a
and 26b are pivotally mount:ed at opposed ends of the
axle 24. As seen in Figs. 1 and 9, the transversal
member 18 defines a central cut-out portion 29 in
which a pair of spaced-apart sleeves 27a and 27b
mounted to the axle 24 are disposed. First and second
diagonal struts 28a and 30a extend respectively from
rear and front end portions of the longitudinally
extending beam 26a to connect the same to the sleeve
27a. Similarly, first and Second diagonal struts 28b
and 30b extend respectively from rear and front end
portions of the longitudinally extending beam 26b to
connect the same to the sleeve 27b. By so pivotally
mounting the longitudinal beams 26a and 26b to the
axle 24, the lateral forces transmitted to the frame
structure of the trailer vehicle 10 by the wheels
thereof are counterbalanced, as will be explained
hereinafter.
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As seen in Figs. 1 and 3 a transversal beam
32 mounts rear wheels 33a and 33b at opposed ends
thereof. The transversal beam 32 is pivotally mounted
to the rear ends of the beams 26a and 26b, as will be
explained hereinafter.
As seen in Figs. 1 and 2, pivot shafts 42a
and 42b are provided at the front ends of beams 26a
and 26b and mount wheel mounting beams 44a and 44b,
respectively. A pair of wheels 46a and 46b are
journaled to axles 47a and 47b extending laterally
from the rear ends of the wheel mounting beams 44a
and 44b while a transversal mounting beam 48,
provided at opposed end thereof with wheels 50a and
50b, is pivotally mounted to the front ends of the
wheel mounting beams 44a and 44b.
As seen in Figs. 4 and 5, the beam 48 is
connected to the front ends of the beams 44a and 44b
by means of hinged brackets 34a and 34b respectively
pivoted at pivot pins 36a and 36b in respective lost-
motion slots 38a and 38b defined in the
longitudinally extending beams 44a and 44b,
respectively.
Alternatively, the lost-motion slots 38a
and 38b may be defined in the hinged brackets 34a and
34b and the pivot pins 36a and 36b may extend
transversally through circular holes defined at the
front ends of the longitudinal extending beams 44a
and 44b, as seen in Fig. 5a.
Guide members 40a and 40b, as shown in Fig.
3, enable the ends of the beams 44a and 44b to sit
properly in the prescribed location on the
transversal mounting beam 48. The hinged brackets 34a
and 34b allow some independent movement of the front
wheels 50a and 50b relative to each other.
It is noted that the transversal beam 32 is
pivotally mounted to the rear ends of the beams 26a
and 26b in a manner similar to that just described
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with respect to the transversal mounting beam 48.
Accordingly, the wheels 33a, 33b, 46a, 46b, 50a and
50b will operate independer.itly on either side of the
trailer vehicle 10.
As seen from Fiqs. 1 and 9, the lateral
distance between a first vertical plane passing
through the wheels 33b, 46b and 50b disposed on the
left side of the frame and a second parallel vertical
plane passing through the pivot 42b is substantially
equal to the lateral distance separating the second
vertical plane from a third parallel vertical plane
extending through the left sleeve 27b, thereby
counterbalancing the lateral forces which are exerted
on the frame of the trailer vehicle 10. As the
trailer vehicle 10 is symmetrical relative to the
longitudinal axis thereof, the lateral forces exerted
on the right side of the frame are also
counterbalanced.
Fig. 2 shows how the mass M carried by the
trailer vehicle 10 is distributed to enhance the
suspension characteristics thereof. In accordance
with the illustrated embodiment, the pivot shafts 42a
and 42b and the rear wheels 33a and 33b are disposed
such as to respectively support about 62% and 38% of
the mass applied at the axle 24. About 60% of the
mass supported by the pivots 42a and 42b is
distributed to the wheels 46a and 46b, the remaining
portion of the mass supported by the pivots being
distributed to the front wheels 50a and 50b. However,
satisfactory results have been obtained by
distributing about 60 to 70% of the mass supported by
the axle 24 to the pivot shafts 42a and 42b, the rear
wheels supporting the remaining portion of the mass
carried by the trailer veh_Lcle 10. In this case, the
wheels 46a and 46b may support about 50 to 70% of the
mass distributed to the pivot shafts 42a and 42b.
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The maj or portion of the mass M is
distributed to the rear wheels 33a and 33b to
minimise the percentage of' the mass M supported by
the front wheels 50a and 50b, thereby preventing the
latter from sinking in the soil when the trailer
vehicle 10 is displaced on a soft surface. Thus the
trailer vehicle 10 can move easily over soft ground.
As seen in Fig. 1, a spring mechanism is
provided at each rear end of the beams 26a and 26b
and at each front end of t:he wheel mounting beam 44a
and 44b for eliminating or at least attenuating the
noise resulting from the collision of the beams
26a,26b and 44a,44b against the transversal wheel
mounting beams 32 and 48, respectively. As all the
above mentioned spring mechanisms or noise
attenuating devices 52 are similar, only one of such
devices will be described.
Figs. 4 and 5 illustrates a noise
attenuating device 52 provided at the front end of
the wheel mounting beam 4=4b. The noise attenuating
device 52 includes a spring 54 mounted on a pin 56. A
L-shaped front plate 59 is provided on the front end
of the beam 44b and includes a flange 58. The pin 56
passes through a hole defined in the flange 58. The
wheel mounting beam 48 includes a bracket 60. The pin
56 also passes through a hole defined in bracket 60.
A retaining ring 62 and a first nut 64 are provided
at an upper end of the pin 56 to hold the spring 54
in compression against the upper surface of the
flange 58. A nut 66 is threadably engaged with a
lower end of the pin 56 and urges against an under
surface of the bracket 60 to normally prevent the
transversal wheel mounting beam 48 from pivoting away
from the beams 44a and 44b. However, as the retention
force of the spring is less than the cumulative
weight of the transversal beam 48 and of the wheel
50b, the transversal beam 48 will be subject to
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limited pivot movement relative to the beams 44a and
44b to maintain the wheels 50a and 50b in contact
with the soil, as seen in Fig. 5.
Referring now more specifically to Figs. 1,
6 and 7, there is shown a steering mechanism which is
responsive to the direction of movement of a motive
vehicle, such as a tracizor, pulling the trailer
vehicle 10.
The articulated axle assembly of the rear
wheels 33a and 33b and thE: front wheels 50a and 50b
is provided as being at the ends of transversal wheel
mounting beams 32 and 48, respectively.
More particularly, as seen in Fig. 3, the
transversal wheel mounting beam 32 is provided at
opposed ends thereof with bearing brackets 70a and
70b which support respective hinge pins to which
bearings 72a and 72b are journaled. The wheel axles
74a and 74b are fixed to bearings 72a and 72b.
Similarly, the transversal wheel mounting
beam 48 is provided at opposed ends thereof with
bearing brackets 76a and 76b which support respective
hinge pins to which bearings (not shown) are
journaled. Similar to the rear wheel axles 74a and
74b, the front wheel axles 78a and 78b are fixed to
the bearings.
There will now be described the mechanical
system which is used to steer the wheels 33a, 33b,
50a and 50b.
As seen in Figs. 1, 6 and 7 the hitch pole
20 is provided with a forward articulated extension
80 adapted to be coupled to a towbar B of a motive
vehicle. More particularly, the forward articulated
extension 80 includes an articulated member 81 which
is pivotally mounted to a U-shaped front portion 82
of the hitch pole 20 for rotation about a vertical
axis. As seen in Fig. 7, the U-shaped front portion
82 is fixedly mounted on a shaft 83 which is in turn
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pivotally mounted in the longitudinal axis of a tube
85 secured to the V-shaped portion of the hitch pole
20. The U-shaped front portion 82 and the articulated
member 81 define a vertical passage through which a
lock pin 84 may be inserted to attach the towbar B
which is disposed between the legs of the U-shaped
portion 82 of the trailer vehicle 10, as seen in Fig.
7.
The articulated nlember 81 is provided at a
front end thereof with a pair of downwardly extending
pins 86a and 86b which are disposed to receive
therebetween the towbar B of the motive vehicle.
Thus, when the motive vehicle will turn to the left,
the articulated member 8:1 will be rotated in a
counterclockwise direction about the pivot axis of
the lock pin 84. If, the motive vehicle turns to the
right, the articulated mernber 81 will rotate in a
clockwise movement. The articulated member 81 is
provided with a hinge 88 having a longitudinal axis
to facilitate connection of the articulated member 81
to the drawbar B of the motive vehicle.
The articulated extension 80 further
comprises a parallelogram linkage 92 for conveying
the motion transmitted to the articulated member 81
by the motive vehicle to a pivot assembly 90 mounted
to the hitch pole 20. More specifically, the linkage
includes a pair of link rods 94a and 94b. Ball joints
93a and 93b are provided for connecting the front
ends of the link rods 94a and 94b to a pair of arms
96a and 96b extending laterally from the articulated
extension 80. A plate 98 secured to a pivot shaft 100
is connected at opposed ends thereof to the rear ends
of the link rods 94a and 94b by means of ball joints
95a and 95b. The ball joints 93a, 93b, 95a and 95b
allow a rotation of about 20 degrees of the U-shaped
portion 82 with the shaft 83 about the longitudinal
axis thereof.
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As seen in Fig.. 6, the front ends of the
link rods 94a and 94b are equidistant from the pivot
axis of the articulated extension 80, while the rear
ends thereof are equidistant from the rotating axis
of the pivot shaft 100. Therefore, when the
articulated member 81 rotates in a counterclockwise
direction, the pivot shaft 100 will rotate in the
counterclockwise direction. Similarly, if the
articulated member 81 rotates in a clockwise
direction, the pivot shaft 100 will rotate in the
clockwise direction.
The pivot shaft 100 is connected to an
axially extending steering shaft assembly 102 by
means of a gear box 104 adapted to couple
intersecting shafts. As shown in Fig. 1, the gear box
104 is configured to transfer the direction of
rotation of the pivot shaft 100 to the shaft assembly
102.
The steering shaft assembly 102 includes a
number of shaft sections mounted in an end to end
relationship by means of ur.Liversal joints in order to
accommodate relative changes in altitude between the
frame portions forming the frame structure of the
trailer vehicle 10.
More particularly, a universal joint 105
connects the first shaft section 106 to a second
shaft section 108 supported under the main frame 12.
A second universal joint 110 connects the second
shaft section 108 to a third shaft section 112
connected at the opposed end thereof to a fourth
shaft section 114 by means of joint 116 and the
fourth shaft 114 is jour=naled to the transversal
wheel mounting beam 48. A universal joint 118 is
provided for connecting the fourth shaft section 114
to a fifth shaft section 120 connected at the opposed
end thereof to a sixth shaft section 122 by means of
the universal joint 124. The sixth shaft section 122
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is supported under the transversal member 18 and is
connected at opposed end thereof to a seventh shaft
section 126 by means of the universal joint 128.
Finally, a universal joint 130 connects the seventh
shaft section 126 to a eighth shaft section 132
supported by the transversal wheel mounting beam 32.
As seen in Fig. 10, a plate 134 acting as a
crank is mounted on the fola.rth shaft section 114 for
rotation therewith. A first link rod 136a is
connected at a first end thereof to the plates 134
and at a second end thereof to a steering arm 138a
extending forwardly from !:he bearing to which the
front wheel axle 78a is secured. Similarly, a second
link rod 136b is connected at a first end thereof to
the plate 134 and at a second end thereof to a
steering arm 138b extending forwardly from the
bearing to which the front wheel axle 78b is secured.
The first ends of the link rods 136a and 136b are
equidistant from the rotating axis of the fourth
shaft section 114. The lirik rods 136a and 136b are
connected to the plate 134 and the steering arms 138a
and 138b by ball joints.
As seen in Fig. 1, when the steering shaft
assembly 102 is rotated in the counterclockwise
direction in response to a left turn of the motive
vehicle, the link rods 136a and 136b are laterally
displaced, thereby causing the front wheels 50a and
50b to pivot in the direction the motive vehicle
steers to trace an arc sirnilar to an arc traced by
the motive vehicle.
It is understood that in the event that the
gear box 104, provided for connecting the pivot shaft
100 to the steering shaft assembly 102, transmit a
rotation to the shaft assembly 102 in a direction
inverse to the direction of rotation of the pivot
shaft 100, the steering arrns 138a and 38b, the plate
134 and the link rods 136a and 136b would be disposed
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behind the front wheels 50a and 50b, rather than in
front, to steer the front wheels in the same
direction as the motive vehicle turn.
It is also noted that since the first ends
of the link rods 136a and 136b are equidistant from
the rotating axis of the fourth shaft sections 114,
the lateral displacement of the link rod acting on
the wheel which is located at the exterior of the arc
traced by motive vehicle, will be slightly greater
than that of the other link rod, thereby improving
the lateral stability of the trailer vehicle 10 when
turning.
The steering cont.rol of the rear steerable
wheels 33a and 33b, as shown in Figs. 1 and 3, is
accomplished by means of a pair of link rods 142a and
142b extending laterally from a plate 140 mounted on
the steering shaft assembly 102 for rotation
therewith. The link rods 142a and 142b are connected
at opposed ends thereof to steering arms 144a and
144b extending rearwardly from bearings 72a and 72b.
Thus, as seen in Fig. 1, when the steering shaft
assembly 102 is rotated in the counterclockwise
direction in response to a left turn of the motive
vehicle, the link rods 142a and 142b are laterally
displaced, thereby causing the rear wheels 33a and
33b to pivot in the opposite direction the motive
vehicle steers to trace an arc similar to an arc
traced by the latter.
It is understood that in the event that the
gear box 104, provided for connecting the pivot shaft
100 to the steering shaft assembly 102, transmit a
rotation to the shaft assembly 102 in a direction
inverse to the direction of rotation of the pivot
shaft 100, the steering arms 144a and 144b, the plate
140 and the link rods 142a and 142b would be disposed
in front of the rear wheels 33a and 33b, rather than
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behind, to steer the front wheels in the opposite
direction of the motive vehicle turn.
However, in any case, the front steering
arms 138a, 138b and the rear steering arms 144a, 144b
must always extend in opposite directions to ensure
that the front wheels 50a, 50b and the rear wheels
33a, 33b pivot in opposite directions. Indeed, if the
front steering arms 138a arid 138b extend in front of
the front wheels 50a and 50b, the rear steering arms
144a and 144b will extenci rearwardly of the rear
wheels 33a and 33b, and vice versa.
As seen in Figs. 1 and 3, springs 146a and
146b are provided between vertical plates 148a and
148b extending from the top surfaces of the rear
steering arms 144a and 144b and bracket 149a and 149b
extending rearwardly from the bearing brackets 70a
and 70b. The springs 146a and 146b act as stabilisers
and also provide assistance in returning the wheels
33a and 33b to their original position parallel to
the longitudinal axis of the trailer vehicle 10,
wherein the same is displaced in a linear direction.
As seen in Fig.. 1, the front steering
wheels 50a and 50b are also provided with spring
stabilising units. More specifically, springs 150a
and 150b are mounted between first brackets 152a and
152b extending rearwardly f:rom the bearings to which
the front wheel axles 78a and 78b are mounted and
second brackets 154a and 154b mounted to a rear side
of the bearing brackets 76a and 76b.
Fig. 8 illustrates an alternative linkage
system which may be used to steer the rear wheel 33a
and 33b of the trailer vehicle 10. The linkage system
comprises a first link rod 156 connected at a first
end thereof to the plate 140 and at opposed end
thereof to the rear steeririg arm 144b. A second link
rod 158 extends between the steering arms 144a and
144b to form a parallelogram linkage, thereby
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ensuring parallel movement of the rear wheels 33a and
33b.
Referring to Fig. 11, there will now be
described a second embodiment of the steering
mechanism of the present invention.
Instead of using a rotatable steering shaft
assembly as described hereinbefore, a system of links
and cranks may be used to connect the articulated
member 81 to the front and rear steerable wheels 33a,
33b, 50a and 50b.
More specifically, as schematically
illustrated in Fig. 11, a parallelogram linkage 202
is provided for conveying the motion transmitted to
the articulated member 81 by the motive vehicle to a
crank assembly 204 mounted the transversal wheel
mounting beam 48. The crank assembly 204 includes a
substantially horizontal plate 206 mounted for
rotation about an upwardly extending pivot 208
connected to the wheel mounting beam 48.
The linkage 202 rnay include a pair of rods
210a and 210b having front ends connected to arms 96a
and 96b extending latera:Lly from the articulated
member 81, and rear ends connected to the plate 206.
Therefore, when the articulated member 81 rotates in
a counterclockwise direction, as illustrated in Fig.
11, the plate 206 will rotate in the counterclockwise
direction.
A first link rod 212a is connected at a
first end thereof to a front portion of the plate
206, i.e. in front of the :pivot 208, and at a second
end thereof to the steering arm 138a. Similarly, a
second link rod 212b is connected at a first end
thereof to the front portion of the plate 206 and at
a second end thereof to the steering arm 138b.
The link rods 212a and 212b may be
connected to the plate 206 and the steering arms 138a
and 138b by ball joints or the like.
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As seen in Fig. 11, when the plate 206 is
rotated in the counterclockwise direction in response
to a left turn of the motive vehicle, the link rods
212a and 212b are late.rally displaced, thereby
causing the front wheels 50a and 50b to pivot in the
direction the motive vehicle steers to trace an arc
similar to an arc traced by the motive vehicle.
A second pair of links 214a and 214b
connect the plate 206 to a second crank assembly 216
mounted to a bracket 217 extending rearwardly from
the transversal wheel mounting beam 32. The second
crank assembly 216 includes a substantially
horizontal plate 218 mounted for rotation about a
pivot 220 extending upwardly from the bracket 217.
Thus, the links 214a and 214b will convey
the motion transmitted to the plate 206 by the
articulated member 81 to the plate 218 of the second
crank assembly 216. Indeed, as seen in Fig. 11, when
the plate 206 is rotated in the counterclockwise
direction, the plate 218 is also rotated in the
counterclockwise direction.
A first link rod 222 is connected at a
first end thereof to a front: portion of the plate 218
and at a second end thereof to the steering arm 144b
extending rearwardly from the wheel pivot assembly of
the wheel 33b. A second link rod 224 extends between
the steering arms 144a and 144b to form a
parallelogram linkage, thereby ensuring parallel
movement of the rear wheels 33a and 33b.
By connecting the link rod 222 to a front
portion of the plate 218 and to the steering arm
144b, which extend rearwardly from the pivot of the
rear wheel 33b, the rear wheels 33a and 33b will
rotate in a direction opposite to that of the front
wheels 50a and 50b, thereby enabling the trailer
vehicle 10 to trace an arc similar to an arc traced
by the motive vehicle. For instance, the
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counterclockwise rotation of the articulated member
80 will cause the counterclockwise rotation of the
plates 206 and 218, thereby causing the link rod 222
to push on the steering arm 144b to steer the rear
wheels 144a and 144b in a direction opposite to the
motive vehicle turn.
It is understood that the links 210a, 210b,
214a and 214b may include a number of link sections
connected in an end to end relationship by attachment
suitable to accommodate relative motions between the
various frame portions forming the frame structure of
the trailer vehicle 10. Furthermore, the links 210a,
210b, 214a and 214b may also be provided in the form
of cables.
Furthermore, it is, also understood that the
forward articulated extension 80 may include a system
of cables or chains extending between the motive
vehicle and the pivot assernbly 90 or the plate 206
instead of the above described articulated member 81.
For instance, a parallelogram linkage could be used
to transmit a change of direction of the motive
vehicle to the pivot assembly 90 or the plate 206.
Figure 12 illustrates another construction
of the present invention wherein the pivot assembly
90 is mounted to the transversal member 15 by means
of a bracket 226 instead of being mounted to the
hitch pole 20 as described hereinbefore.
Finally, although the present invention has
been described in the context of a trailer vehicle
having three sets of wheels, it is understood that
the present invention may be used in connection with
a trailer vehicle having morle or less than three sets
of wheel s .
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